Tag Archives: polar bear

Global polar bear population size is about 26,000 (20,000-32,000), despite PBSG waffling

The IUCN Polar Bear Specialist Group admits its global population estimate is simply a qualified guess with a large potential error.  So perhaps it’s time to acknowledge that for the purpose of comparing polar bears to other species of concern, the upper limit for polar bear numbers worldwide could be more than 30,000?

Polar bears USFWS_cover PolarBearNews2013_2014

See previous posts on this global population size issue (here and here); updated information below, including the most recent IUCN PBSG statement.

UPDATE 1 September 2015: here is an updated graph of polar bear population numbers that undo the “subtractions” of the PBSG between 2001 & 2013, giving a final global estimate of about 26,000. Click to enlarge:

Crockford unofficial polar bear numbers to 2015 Sept 1 FINAL

UPDATE 25 November 2015: The 2015 update of the IUCN Red List for polar bears essentially concurs with my assessment about polar bear numbers. They estimate the current global population is 20,000-31,000 (average of 25,500, see below, without considering the number of bears in the Arctic Basin, so not far off my assessment) but say the trend in the population is “Unknown.”

Crockford OFFICIAL polar bear numbers to 2015_IUCN concurrs Nov 18

UPDATE 23 February 2017: A new population estimate update is available based on three new survey counts that add about 2,000 bears to the average total, bringing it to almost 30,000 (28,500). Details here.

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Hudson Bay sea ice coverage is atypical this year but what does that mean for polar bears?

Churchill_Polar_Bear_2004-11-15 Wikipedia

There is a rather large patch of open water in the northwest sector but what’s also unusual about breakup this year is the virtual lack of open water in eastern Hudson Bay – that almost never happens (compare to 2013 here). In addition, there’s still very little open water in Hudson Strait, which connects Hudson Bay to Davis Strait in the east – that’s also unusual.

Figure 1.  Sea ice extent over Hudson Bay and Hudson Strait at 26 May 2015. Canadian Ice Service.

Figure 1. Sea ice extent over Hudson Bay and Hudson Strait at 26 May 2015. Canadian Ice Service. Click to enlarge.

The question is: does the somewhat unusual pattern of ice cover at this date – which developed rapidly over the last few weeks – suggest we can predict whether polar bears will have a shorter-than-average hunting season?

To answer that, you have to look at maps generated by the same source over several years. The result, in my opinion, is inconclusive – while so far, this year looks a bit more like 2009 (which was a very late sea ice breakup year) than it does 2011 (which was an early breakup year), it’s really too early to tell.

I suggest we simply won’t know for another month or so which pattern will prevail. However, that hasn’t stopped IUCN Polar Bear Specialist Group member Andrew Derocher (via Twitter, e.g., here and here, among many others) from suggesting that this year’s pattern is likely a portend of doom for Hudson Bay polar bears. See what you think.
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University newspaper misleads readers on status of Western Hudson Bay polar bears

Even though polar bear experts admit there has been no trend in sea ice breakup or freeze-up dates since 2001 – and both Canadian and International experts say this subpopulation is stable – the public is still being misled about the status and condition of polar bears in Western Hudson Bay.

WHB status 2015 IUCN PBSG_PolarBearScience

The latest example of misinformation about Western Hudson Bay polar bears appears in a feature story carried by the campus newspaper of York University (Ontario, Canada), meant to highlight the work of biology graduate student Luana Sciullo.1
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Polar bear habitat update: Hudson Bay sea ice breakup on track

Hudson Bay sea ice coverage is only slightly below average for this time of year (week of 14 May, below) but well above levels for 2006, when Western Hudson Bay breakup was relatively early).

Sea ice Canada 2015 May 14_CIS

Figure 1. Sea ice coverage over Hudson Bay for the week of 14 May, 1971-2015. Canadian Ice Service. Click to enlarge.

Figure 1. Sea ice coverage over Hudson Bay for the week of 14 May, 1971-2015. Canadian Ice Service. Click to enlarge.

Even at its highest extent in April, Hudson Bay is only 97-98% ice covered (due to persistent shoreleads and polynyas), which means ice levels are currently only 10% or so below maximum. In other words, there is still lots of polar bear hunting habitat over the bay.

That’s a bit lower than ice coverage was for the last two years at this date (2013-2014), which had average or above average ice cover. However, there is currently a bit more ice on Hudson Bay than there was in 2011 and 2012 – and much more than there was in 2010 and 2006.
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Snow depth over spring sea ice affects polar bear feeding success and ringed seal survival

Snow depth over sea ice in spring affects the hunting success of polar bears on ringed seal (Phoca hispida) pups, but the relationship is more complicated than you might think and there is less data on this phenomenon than you would believe.

Ringed seal lair_snow and ice thickness_PolarBearScience_sm

Regional snow depth in spring (April-May) varies naturally from year to year due to weather patterns driven in part by long-term climate cycles (like the Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation, and the Arctic Oscillation).

This year, it was very cold in Eastern North America, with record-breaking snow fall in some areas. Snow depth was apparently greater than average over Hudson Bay sea ice this spring but was it deep enough to have impaired polar bear hunting success?

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Labrador polar bear not lost or in danger – just running down a rural highway

An interesting report from Labrador this morning: video footage of a fat polar bear running down an isolated 2-lane highway in southern Labrador.

Cartright Junction_Labrador pb_Chelsea Morris photo from video

Yet another reminder that there is still a lot of sea ice off that coast, which is home to the Davis Strait polar bear subpopulation.
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Polar bear habitat update – sea ice for hunting plentiful in all subpopulation regions

Preferred polar bear habitat is said to be 50% concentration or higher over continental shelves, which describes all but the fringes of sea ice extent today, including Hudson Bay, the Southern Beaufort, and the Barents Sea.

Preferred polar bear habitat 50pc concentration_May 8 2015_PolarBearScience

However, polar bears – excellent swimmers that they are – are quite capable of utilizing areas with 15-50% sea ice concentration if necessary (Durner et al. 2004; Rode et al. 2014:79), especially when prey are plentiful.  This would account for the fact that there are still sightings of polar bears in and around northern Newfoundland (see previous post here and photo below1), where ice concentration is in the 30-50% range.

Photo with this news story (7 May 2015): "(Update) Polar bear sighting in Croque"

Photo with this news story (7 May 2015): “(Update) Polar bear sighting in Croque”

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Designated critical habitat for Alaskan polar bears offers no protection from thick spring ice deaths

The Obama administration is apparently attempting to overturn a previous ruling that rejected proposed Alaskan “critical habitat” for polar bears in 2013 – as if “critical habitat” would protect the bears from the repeated episodes of thick spring ice that develop in this region every 10 years or so.

Polar_Bear_male on sea ice_Alaska Katovik Regehr photo_April 29, 2005_sm labeled

According to a Reuters report today (5 May 2015):

Seeking to reverse a ruling throwing out its designation of critical habitat for polar bears, the Obama administration has defended its decision to list large swathes of the Arctic as necessary for the conservation of the threatened species.

A coalition of oil industry groups and Alaska Natives, represented by Stoel Rives and Holland & Hart, successfully persuaded the U.S. District Court for Alaska to vacate the government’s polar bear habitat designation in 2013.” [my bold]

If they succeed, it would put most of the north coast of Alaska under special ESA rules, as the map below shows (click to enlarge).

Critical habitat Polar Bears US_NorthSlopeOrg map_labeled_PolarBearScience

As I commented previously, regarding the Obama administration’s recommendation to congress that they approve a proposed Arctic wildlife refuge area on Alaska’s North Slope, this move (if implemented) would not protect polar bears from the starvation deaths due to thick spring ice conditions that have occurred in this region for 2-3 years out of every 10 since 1960 at least.

The other issue is how much additional, biologically meaningful protection a critical habitat designation would provide for Southern Beaufort and Chukchi Sea polar bears – over and above that already provided by the Marine Mammal Protection Act.
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Polar bear season for Newfoundland residents still going strong, recent sightings confirm

Two recent sightings of polar bears along the north shore of Newfoundland are a reminder that sea ice is still a prominent feature of the Davis Strait polar bear subpopulation landscape at this time of year.

LaScie_Newfoundland_April 27 2015_ColleenGray label

A polar bear was sighted in the community of La Scie, northern Newfoundland Monday, 27 April (pictured above, swimming in the harbour), while another landed in the town of Fogo, on Fogo Island, last week (see maps below).
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Polar bears barely survived the sea ice habitat changes of the last Ice Age, evidence suggests

While the polar bear is an Ice Age species, genetic and fossil evidence suggests it barely survived the profound sea ice changes associated with the Last Glacial Maximum, one of the most severe glacial periods of the Pleistocene.

polar_bear_usfws_no date_sm

A map of sea ice extent at the climax of the Last Glacial Maximum (both perennial and seasonal ice), prepared with the help of a colleague, makes it possible to discuss what genetic and fossil evidence can tell us about the probable effects of glacial conditions on polar bears and ringed seals.

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